Process for preparing layers of acetyl cellulose for coating materials



UNITED STATES PATENT OFFICE.

ARTHUR EICHENGRUN, or RRRLIneE'RMAnY, ASSIGN'OR, BY MESNE ASSIGNMENTS, T0 AMERICAN CELLONE COMPANY mo), 01? NEW YORK, n. Y., A CORPORATION OF NEW YORK.

PROCESS FOR PREPARING LAYERS 0F ACETYL CELLTILOSE FOR COATING MATERIALS.

Patented Nov. 2, 1920.

No Drawing. Application filed April 11, 1910, Serial No. 554,809. Renewed April 2, 1920. Serial No.

To, all whom it may concern Be it known that I, ARTHUR EIoHENeRiiN, Ph. D., of 87 Konstanzerstrasse, Berlin, in the Kingdom of Prussia and German Empire, have invented new and useful Improvements in Processes for Preparing Layers of Acetyl Cellulose for Coating .Materials.

, Hitherto the production of acetyl cellulose layers with fiat or smooth surfaces upon layers of fibers, fabrics, leather and the like could not be effected on a manufacturing scale, because solutions ofacetyl cellulose, especially those with additions for rendering the latter plastic or soft, do not dry up to a flat surface, but adapt themselves to the structure of the fiber or the like material, or completely enter into the same, as is the casewith fabrics of large meshes. The production of flat coatings can be obtained, it is true, by first making thin sheets of acetyl cellulose, and then gluing I the same on to the fabrics previously moistened with a solvent. Hitherto this method, however, had the disadvantage that the thin sheets soften and lose their flat surface with the least excess of solvent, and further that they can only be' manufactured and worked in a certain thickness. In consequence of this the acetyl cellulose coatings become too heavy and too expensive, quite apart from the fact that in this manner only comparatively small surfaces canbe worked.

Now I have found that these difliculties of manufacture and these sources of defects can be obviated if the thin layers of acetyl cellulose are brought into contact with the materials to be coated by means of a suitable A prevents a I change of foundation, which their surfaces.

For this purpose the solutions of acetyl cellulose are spread on fiat, flexible lengths of a suitable material, 'as for instance on strips of thin sheets of tin, metal paper, waxed cloth, rubber fabric, patent leather, glazed linen, etc., from which, after drying they loosen themselves automatically with-- out difliculty in the form of thin sheets.

On this foundation they are then, either directly after pouring on the solution or after drying, brought into contact, preferably under a slight pressure, with the material to be coated, which, if desired, may be moistened with a solvent, or may be warmed. As in this manner sheets of acetyl cellulose of unlimited length and of very small thickness can be made for instance on a metal paper. foundation, it is easily possible to coat by means of the said lengths, also great lengths of fabrics, by passing the metal paper lengths carrying the layer of acetyl cellulose, together with the lengths of the fabrics through a pair of rollers under moistening or warming the length of fabric, whereby the layerv of acetate combines with the fabric-and after drying automatically loosens itself-on unrolling from the length of paper." According to the fact whether the foundation used for the acetate solutions has a brilliant, frosted or patterned surface, also the surface of the acetate layer, be it that the same is peeled off as a thin sheet or transferred to a length of fabric, becomes brilliant, frosted or patterned. Naturally one can also proceed in such manner that for the foundation as well as for the carrier a material of the same kind is used if the adhesion of. the dry layer of acetate to the carrier is prevented by a suitable preparation of the latter. For instance a layer of acetate, showing the natural creases of leather can be obtained on undressed leather by coating upper leather, which may be previously covered with a thin layer of hard resin, or finished patent leather with a solution of acetate, and by bringing it, before complete drying of the latter, into intimate contact with the undressed leather by means of a press or by means of. hot pressure rollers. After the complete drying the layer of acetate adheres firmly 'to the undressed leather and 'can be easily removed from the leather serving as carrier, the structure of which it has accepted and maintained.

The new method proves itself especially valuable for the manufacture of coatings of acetate upon very soft, porous and feltlike materials, as well as upon fabrics of wide meshes, as for instance tulle, gauze and the like, for which the manufacture of a smooth coating in lon lengths was hitherto completely impossib e.

Polished or the like layers of acetyl cellulose upon paper, cloth, leather, metal and other suitable materials can according to --my presentinvention also be obtained by employing solutions of acetyl cellulose in mixturesof alcohols and hydrocarbons or the like. described in my British Letters Patent X0. 1%41/10, the solutions which are being used can if desired,.be obtained by cold acting solutions. such as obtained in the presence of acetone and the like solvents for acetyl cellulose, or non-dissolving liquids for acetyl cellulose, such as water.

In the above-mentioned Letters Patent, solutions have been described obtained by treating suitable acetyl cellulose in the presence of camphor substitutes under heating in mixtures of alcohols and hydrocarbons or other liquids which do not dissolve acetyl cellulose when cold. or by mixing concentrated solutions of acetyl cellulose in ace:

tone, ethyl acetate, acetylene tetrachlorid, 'epichlorhydrin and the like with mixtures of alcohols and hydrocarbons and the like.

These solutions which partly are liquid only when hot, but partly also when cold, have proved to be extremely suitable for providing fibrous materials, cloths, leather, wood, metal and the like or articles made of any other material with a varnished or enamellike surface coating of acetyl cellulose. On account of the facts that solutions which are liquid only when hot directly solidify when cooling down and that the solutions which are liquid when cold possess a very high degree of viscosity, it is not only possible to apply acetyl cellulose coatings to a relatively porous material, such as for instance cotton fabrics in smooth layers, but also to obtain layers of acetate of considerable thickness and smooth surface upon little porous surfaces,'such as upon leather. This was not possible with the hitherto known acetyl cellulose solutions in chloroform, acetone, ethyl acetate and the'like, because the concentrated solutions always showed the disadvantage that numerous air-bubbles formed themselves in consequence of the formation of a surface skin, p'reventingthe evaporation of the solvent from. the lower layers, whereas weak solutions are free from bubbles, but quickly dry off-under the formation of a strong surface structure, and have to be painted on several times for obtaining a sufficiently thick layer of acetate.

These difliculties are entirely avoided when employing the new solutions and perfectly regularly drying layers free from blisters can be obtained by simply pouring on the solutions as well as by painting them by means of a brush, a simple lacquering machine or other usual: mechanical arrangement.

The above described solutions do not enter into the poresbut remain on the surface of the articles or materials to be coated, so

the above mentioned mixtures are mixed Wltl1 small amounts of cold-acting solvents or with water. glycerin and its esters and the like, such as for instance a solution of acetyl cellulose and guaiacol in alcohol-benzol with 10% of acetone and 10% water. These solutions remain liquid exceptionally long, and therefore, only dry very slowly and very regularly, and thus in their behavior correspond in spite of the. low boiling point of the components to a solution in a solvent of high boiling point, which up to now has not yet been found for acetyl cellulose. As also the layers obtained from the hot liquid solutions, for instance alcohol-benzol, only dry slowly in so far as the layer resulting when solidifying only represents a solid solution giving off the solvent only slowly, thesddacquer layers before drying can easily be provided with a very bright polish by pressing them against brilliant surfaces, or by satinating them by means of polished rollers, if desired under heating.

Hereby the surface of the rigid solution is brought to melt and by means of this a high polish, and when employing calander rollers any desired patterns are obtained.

It is important to note that solutions of acetyl cellulose made with simple solutions, such as have been heretofore proposed, are very thin liquids and therefore do not give a coating but on the contrary sink into the materials and thereby harden the same. If for example concentrated solutions are taken, made with solvents such as those heretofore proposed such as a 20 per cent. acetone solution, that part of the solution which remains at the surface will dry superficially while in the interior thesolution will remain soft and on the evaporation of the acetone in the interior countless little blisters will be produced. According, however, to the present invention there are obtained'solutions of high viscosity whereby coatings of any desired thickness can be formed with the most convenient tools or other means for applying same such as lacquering machines, rolling machines, spreading knives, spraying apparatus or the like as well as dipping the materials in the solution. When using such solutions as have een heretofore proposed, these can only be used in a thin state and therefore thicker and absolutely waterproof solutions can only be formed by repeated operations.

What I claim as new and desire to secure by Letters Patent is: r i

1. A process of preparing a solution of acetyl cellulose consisting in treating acetyl cellulose in .the cold with a cold acting sol vent for said acetyl cellulose and with a sol vent which only dissolves said acetyl cellulose when heated;

2. A process of preparing a solution of acetyl cellulose consisting in treating acetyl cellulose in the cold with a cold acting solvent for said acetyl cellulose, a solvent acting onlyv in the Warm on said acetyl cellulose, and a non-solvent for said acetyl cellulose; I

A process of preparing a solution of acetyl cellulose consisting in treating acetyl cellulose in the cold with a cold'acting solvent for said acetyl cellulose and a mixture of two non-solvents for said acetyl cellulose which have a solvent action on same when heated.

cellulose with a solvent for said acetyl cellulose and a mixture of a non-solvent for said acetyl cellulose and a warm acting solvent for same.

5. A process of preparing a solution of acetyl cellulose consisting in treating acetyl cellulose with a mixture of a non-solvent for said acetyl cellulose and a warm acting solvent for same.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

ARTHUR EIOHENGRUN. Witnesses 1 DEAN B. MASON, J ACK H. BAKER. 

